Digital image editing has become increasingly more popular as digital image capture devices have become somewhat ubiquitous. An individual, for instance, may carry a mobile phone, dedicated camera, or the like that the individual can utilize to capture digital images of objects (e.g., landscape, room, sporting event, individuals, etc.) that are of interest. In some instances, these digital images do not capture the scene as desired. In such instances, digital image editing techniques can be employed to modify the digital image to achieve a desired result. One of these digital image editing techniques that is commonly used attempts to relight an image to achieve a desired effect. Conventional relighting techniques, however, are inadequate to achieve a realistic result. This is especially the case with respect to portraits because of the intricacies involved in relighting an object (e.g., a face) in a realistic manner.
Some conventional relighting techniques for portraits attempt to estimate facial geometry, lighting, and reflectance of a face in an image to re-render the face with a desired lighting effect. In these re-rendering based relighting techniques, small errors in the estimated geometry, lighting, or reflectance can lead to artifacts in the resulting re-rendered image. These artifacts can cause the resulting re-rendered image to fail at achieving the desired lighting effect and can also cause the resulting image to appear unrealistic. As such, accuracy in calculating the estimated facial geometry, lighting, and reflectance is important to such techniques. However, increased accuracy can be computationally intensive and cannot fully eliminate these small errors. Consequently, a realistic resulting image can be very difficult to achieve.
Other conventional relighting techniques are filter based and rely on the application of various filters to the image to generate the relit image. Filter-based relighting techniques, however, fail to take into account positional information of the face being relit and, therefore, also often produce unrealistic results.